Apparatus for equalizing the temperature inside exothermic reaction chambers



M. JEAN 2,910,350 EQUALIZING THE TEMPERATURE HEEMIC REACTION CHAMBERSOct. 27, 1959 APPARATUS FOR INSIDE ExoT 5 Sheets-Sheet 1 Filed Feb. 19.1954 A M m A /A m m n M .wu 7 MM Q, T A 1 2 wf E, f was@ 75X@ Ef 1f JITf Mun u .-.nmm O ,A x A isi.

M. JEAN APPARATUS FOR EQUALIZING THE TEMPERATURE oct. 21, 1959 INSIDEEXOTHERMIC REACTION CHAMBERS 5 Sheets-Sheet 2 Filed Feb. 19. 1954 luz/VARC .FL

Oct. 27, 1959 M. JEAN 2,910,350

APPARATUS RoR EQUALIZING THE TEMPERATURE INSIDE ExoTHERuIc REACTIONCHAMBERS Filed Feb. 19. 1954 5 Sheets-Sheet-3 I/v VEA/rafa' MARC ELdEA/v my K Mw Oct. 27, 1959 M. JEAN 2,910,350

APPARATUS FOR EQUALIZING THE TEMPERATURE INSIDE EXOTHERMIC REACTIONCHAMBERS Filed Feb. 19. 1954 5 Sheets-Sheet 4 Oct. 27, 1959 Filed Feb.19. 1954 M. JEAN APPARATUS FOR EQUALIZING THE TEMPERATURE INSIDEEXOTHERMIC REACTION CHAMBERS 5 Sheets-Sheet 5 MA kan dra/V nur UnitedStates Patent Oliice 2,910,350 Fatented Oct. 27, 1959 APPARATUS FOREQUALZNG THE TEMPERA- TURE INSIDE EXOTHERMIC REACTIN CHAM- BERS MarcelJean, Paris, France, assignor to Societe Chimique de La Grande Paroisse,Azote et Produits Chimiques, Paris, France Application February 19,1954, Serial No. ML/199 Claims priority, .application France February23, 1953 4 Claims. (Cl. 23a-289) The present invention relates to amethod for equalizing the temperature inside exothermic reactionchambers, particularly when the reactions are carried out under highpressures and at high temperatures, as, for instance, the synthesis ofammonia from its elements, the synthesis of methanol and the like.

In the French Patent No. 626,501, led April l, 1926, for A Method forEqualizing the Temperature Inside Exothermic Chemical Reaction Chambers,there has been described a method for rendering the temperature asuniform as possible, consisting essentially in heating tofthe reactiontemperature a part of the gases to be reacted by causing them tocirculate rst in indirect contact with the catalyzing material, theninside systems, each consisting of an inner tube opening inside an outertube; the gases circulate inside the outer tube in op posite directionto .the circulation inside the inner tube, and ythe gases issuing fromIsaid outer tube are distributed over the catalyzing material at thevery end of said outer tube which dips into what may be called `theorigin of the catalyzing material, that is to say the portion of thecatalyzing material opposite the exit of said gases from said material.The above tubes, similar to the Fields tubes used in boilers, aredesignated thereafter under the name of bell type tubes. At the sametime, the other portion `of the gases to be reacted having circulatedfor insance around the cartridge containing the catalyzing material,reaches the origin of this material for cooling said origin where thereaction is most violent. The gases then leave this origin of thecatalyzing material, reacting with the Aremainder of the catalyzingmaterial cooled by the bell type tubes as well as by the circulation .ofthe gases outside the cartridge.

While this arrangement gives good results for car- -tridges of smalldimensions, i.e. for low gas outflows, things are dierent in the case ofimportant outflows; the very great amount of heat evolved must besuitably eliminated at all points of the catalyzing material andtransferred to the gas mixture to be reacted for avoiding, on the onehand, a limitation of the production of the synthetic product due to lanunfavorable shifting of the reaction equilibrium at high temperatures,and, on the other hand, for preventing the coalescence of the catanlyzing `material which, when super-heated loses its active dividedcondition and assumes the crystalline condition under which itscatalytic efficiency is very low.

The present invention relates particularly to this case of importantproduction by providing the various cooling means which are necessaryfor equalizing, as well as possi-ble, the reaction temperature all alongthe path of the gases over the catalyzing material, said means beingadapted to the intensity of reaction at the place where they 'are used.

To this end, the method according to the present invention, uses, asknown, in the initial Zone of the reaction, the circulation of the gasmixture to be reacted rst in indirect contact with the catalyzingmaterial, then the circulation in bell type tubes dipping in the sameportions of said material, and uses also the known distribution, overthe origin of said material, of the gas mixture having thus circulatedand issuing rom the end of the annual conduit of the bell type tubes;but said method is characterized in that use is made, for the first oneof these circulations, of not a portion only but of the whole of the gasmixture, already hot, and in that, after this first circulation, thedistribution of this gas mixture is continued over a portion of thecirculation path in the annular conduit of the bell type tubes (thismixture being so distributed over a relatively important length of thecatalyzing material), and in that, v'towards the end of the bell typetube zone, the gases having partly reacted are caused to pass through ,aportion of the .ca-talyzing material cooled by indirect contact withlesser and lesser portions of the gas mixture to be reacted andarriving, in part, in successive portions as -it circulates, withouthaving been heated substantially above the ambient temperature, whilethe other portion has been heated by passing rst in indirect contactwith the output gases, then in indirect Contact with the final portionof the catalyzing material.

The above method is particularly advantageous, specially so withrelatively high gas outputs, when the catalyzing material is arranged intubes Jaround which the gases to be reacted circulate before enteringthe bell type tubes, thereby increasing the exchange area between thecatalyzing material and the gases to be reacted.

On the other hand, in combination or not with the latter arrangement, itis advantageous to constitute lthe catalyzing material with a relativelylittle active material, for instance a coarse grained material or mixedwith inert grains, then With a more active material, for instance uergrained. There may also be used, as a little active catalyst, a catalystwhich has already been used or able to satisfactorily resist tooverheating, and as an active catalyst, a different material which maybe sensitive to heat.

Other arrangements which can be used separately or in combinations, areindicated in the following descrip tion `of an apparatus `and of amodified form of this apparatus given by way of `example for carryingout the present method.

On the diagrammatic accompanying drawings,

Figures 1a and 1b represent, by arranging them along the sametheoretical axis, and with Figure la on top .and Figure 1b lower, anaxial section of a tube apparatus assembly.

Figure 2 is a transverse section along line v1I-II of Figure la.

Figure 3 is a view corresponding to Figure l for a modication of theapparatus of Figures ,la and 1b, in which the catalyzingmaterial isplaced inside an annular chamber.

Figure 4 is a transverse section along line IV-IV of Figure 3.

The apparatus or catalysis tube of Figures la, 1b and 2 comprises, asknown, a pressure resistant outer metal tube 1, and inside said tube and`at a distance apart from its wall, the reaction chamber proper orcartridge 2 `which carries on the outer surface of its wall aninsulating material. This cartridge contains tubes` 3 provided with acatalyzing material over the greater portion .of their length and which`for greater convenience in the drawings have been represented 6 innumber only (see Figure 2j) or AS (Figure 4). Towards their upper end,i.e. in the zone in which the reaction begins, .the tubes 3 are providedwith bell type tubes 4 with an ,inner tube 2.3., .said tubes `4 havingtowards their upper end and over a fairly great length several rows oforifices 5 opening on the catalyzing material 6 which, over the greaterpart of the lengthof the bell type tubes ,4, is of a coarser grain thanthe catalyzing material 7 placed immediately below. Instead of b eingcylindrical the bell type tubes 4 might possibly be conical, the largerdiameter being towards the origin of `the catalyzing material. The heatexchange is thus increased, but the amount of catalyst contained 4in thetubes 3 is less than in the case in which cylindrical bell type tubesare used.

After the zone 7, as represented, or slightly before, i.e. slightlyhigher on the drawing, the cooling action is increased locally byincreasing the number of orifices 20 onV the tube 18 lopening at thelower portion of the catalysis -tube `and extending along the axis ofthe apparatus up to a level which may reach or exceed slightly the levelof the ends of the bell type tubes as shown (Figure la). Possibly, inertsubstances bodies 8, surrounded or not with catalyzing material 9, areprovided, the catalyzing material being coarse grained and the grainsbeing identical, for instance, with those of the catalyzing material 6.In the zone of the material 6, the catalyst consists of `a materialwhich is resistant to overheating. It is desirable to arrange, in thecatalyzing material, bales provided with 'apertures (not shown) shiftedfrom one bale to the next and `fairly close to one another. Thesebattles are also to be found beneath the bodies 8 but they are placedlin tine grained catalyzing material 11, identical, for instance, withthose of the catalyzing material 7. These bales 10 terminatesubstantially at the jlevel where the tubes 3 are possibly surroundedwith a heat insulating material 12. At the lower end thereof areprovided wire gauzes 13 some of which extend in the vertical directionand surround inert material bodies 14. These ywire gauzes may bereplaced by baflles. Other wire gauzes lare arranged facing vert-icalwire gauzes 13 in the space 16 existing between the Vouter wall of thetubes 3 and the inner wall of the cartridge 2. Baifles 17 `are provided,over the greater part of the height of space 16 for ensuring the gascirculation around the tubes 3 in good condition for thermal exchange.These bales may, for instance las shown, consist of a helical winding toa suitable pitch of a continuous tape 17a (Figure 2) around the surfaceof the tubes 3 facing outwards, and a second tape 17b between the axialtube 19 and the surface `of the tubes 3 facing inwards. These two tapes17a and 17b may be notched in order to be applied by their edges againstthe surfaces of the tubes 3 along a helix portion of an appreciablelength. The bafes may also consist of discs or crowns the total surfaceof which occupies an entire cross section of the inner cavity of thereaction chamber 2 and which are perforated yfor the passing of thetubes 3 Kand of the tube 19. In this case, orifices for passing thegases are provided in these discs and placed in positions whichalternate from one disc to the next. Similar baffles 17a and 17b arealso provided in spaces 16a and 16 of the mdified embodiment representedin Figures 3 and 4 and described hereinafter.

Along the taxis of the apparatus is provided on the remainder of itslength, towards its upper portion, the tube 19 containingthermo-electric couples not shown and which give the temperature of thegas mixture at Various points of its path. An electric heatingresistance 24 is arranged towards the upper end of the cartridge 2.

. The apparatus opgates as follows:

The gas mixture to be .reacted arrives for its greatest part through thetube 25 at the upper portion of the apparatus; it is at a temperatureclose to the ambient temperature. It then flows down in the space 26between the -inner wall of the tube 1 and the outer wall of thecartridge 2, to thev lower portion of the apparatus; it heats upgradually during this flowing, but owing to the presence of theinsulating material covering the cartridge 2. it reaches a temperaturewhich does not exceed that at which the ordinary steel of the tube `canwithstand to the working pressure.

The gas mixture, thus heated, goes up in the space 16 where it heats uprapidly in contact with the wire gauzes 15 which are heated by theoutgoing gases circulating in opposite direction in contact with thegrids 13. The thermal exchange is facilitated by the eddies caused bythese wire gauzes which could be replaced entirely or partly by numerousbafes carefully adjusted or tins integral with the metal of the tubes.

When -it reaches the level of the annular space 16 corresponding to theupper end of the exchanger formed by the inert material bodies 14, thegas mixture to be reacted enters a zone where the thermal exchange withthe contents of the tubes 3 is much less intense due to the absence ofbaffles and due to the presence of the heat insulating material 12 sothat the temperature of the gas mixture rises less rapidly than in theformer zone.

Then the gas mixture to be reacted, circulating around the tubes 3 inthe space 16, enters a zone provided with the bales 17 which improvegreatly the thermal exchange of these gases with the contents of thenumerous tubes 3.

But the temperature increase which would result therefrom is opposed bythe gradual introduction of the gas mixture to be reacted arriving atthe vicinity of the ambient temperature through the tube 18 andl issuingthrough the orifices 20. Consequently, the thermal exchange in this zoneis intense but the temperature rise of the gases to be reacted isrelativelyl slow and is effected by limited, small successive increases,being slowed down at the various levels of the orifices 20 of the tube18 yand by the arrivals of the cold gas mixture through ward circulatingin the space 16 through baffles 17 around the tubes 3. The temperatureof the gas mixture continues to rise in a relatively slower manner thanpreviously.

When arrived at the upper portion of the cartridge, the

' gas mixture, the temperature of which is regulated by the 24 used forstarting the reaction.

importance of the gas ilow reaching the bottom of the tube and isindicated by the thermo-electric couples in the tube 19, passes incontact with the electrical resistance It then moves down through thetubes 23 placed in the axis of the bell type tubes 4 and is notsubstantially heated during this displacement due to the high speed offlow of the gas mixture; when it reaches the lower end of these tubes24.it moves upwards while heating up slightly to be distributed throughthe orifices 5 at various levels of the catalyzing material 6.

The reaction, which is easily started at the orifice 5 closest to theend of the cartridge, i.e. the origin of the catalyzing material, owingto the fact that the gas flow admitted at that point is relatively low,takes place at a substantially constant temperature. A superheating ofthe catalyst is avoided between this orifice and the closest orifice dueto the fact that the evolution of heat is relatively small due to thelow flow and is easily absorbed, on the one end, inwards by the coolingsurface of the walls of the bell type tubes 4, particularly when thoseare conical as indicated above, and on the other hand outside by theexternal surfaces of the tubes 3, the more so that the outer surface ofthe latter tubes is cooled by the entirety of the gas mixture to betreated. In addition, the gas mixture coming in contact 'with thecatalyzing material through the small orifices -5 of the lower rows, israpidly mixed with the gases which have already circulated on thecatalyzing material and which are loaded with reaction product; due tothis vfact the speed of the reaction is less and the heating up lesssudden.

An important advantage of this arrangement resides in the fact that theamount of gas mixture going through a given volume of catalyzingmaterial in the zone of the origin of said material is relatively small,which facilitates the starting of the reaction and the maintaining of astable operation.

The successive arrivals of the gas mixture on the catalyzing materialthrough the oriiices 5 cool the gases which are being reacted fromportions placed above each oriiice and the temperature remainssubstantially constant in the catalyzing material, increasing onlyslightly between each one of the incoming levels through the orifices 5of theA successive fractions of the gas mixture which areto react.rl'hisstepped introduction of the gas mixture through the orices 5 has,as a consequence, a spreading of the evolution of heat towards a regionof the catalyzing material where the temperature dilference between thegases being reacted and the gas mixture to be reacted, is larger andconsequently the temperature exchange is easier.

The use, in this zone, of a coarse grained catalyzing material 6offering therefore to the gases a lesser contact area, contributes toavoiding too rapid a temperature rise and at the same time it decreaseslocally the load loss. Further, the use in that region of a catalysthaving a good resistance to super-heating ensures the constancy of thecatalytic action.

In addition, it is possible, if necessary, to equalize the temperatureby extending the tube 18 over a part of the length of the bell typetubes, this tube bringing portions of the gas mixtures substantially atthe ambient temperature, through the orifices 2t).

At the end of the path of the gas mixture over these large grains ofcatalyzing material, an important production of the synthesis product isalready obtained, so that the composition of the gas mixture beingcloser to equilibrium, too rapid an evolution of the reaction is nolonger to be feared nor, consequently, too rapid a temperature rise;this explains why the tubes 3` are provided with a catalyzing material 7the same composition with iine grains, for instance like those usedheretofore.

When the gases circulating over the catalyzing material have reached theends of the bell type tubes, the cooling of the catalyzing material isthen effected only through the outer surfaces of the tubes 3. In orderto substantially avoid an excessive increase of the temperature of thegases to be reacted, in the path which starts from this end, the thermalexchange is improved by the presence of baiies and possibly by adecrease in the amount of the product formed, or even by suppressingthis formation; this is effected by an intense local cooling due to theincrease in the number of oriiices 210 on the inner tube 1S, or possiblyby the cylinders of inert material S of relatively short length. Thesecylinders are or are not surrounded with a coarse grained catalyzingmaterial 9 and might be arranged in several superposed layers betweenlayers of the catalyzing material.

In the path of the gases being reacted which starts from the cylinders8, the heating of the gas is limited by the presence of the numerousbafes 10 which facilitate the thermal exchange, as well as the outsidecooling already mentioned due to the cold gas mixture arriving throughthe central tube 18 and flowing through the apertures 20. This tube 18may be heat insulated, if desired.

In this path, the reaction continues its development at a substantiallyconstant temperature, but it becomes slower and slower as the gascontents approach equilibrium, so that the temperature has a tendency todrop. From this time on, a highly active catalyst is used; the lattermay be fine-grained and have a composition different from that of theprevious catalyst; the essential property required from this linegrained catalyst, which is not subjected to super-heating, is a highreactivity while the essential property of the previous catalyst is aresistance to super-heating and to the action of catalyst conltaminators. The eiiciency of the thermal exchange is decreased bysuppressing the bafdes and surroundingthe tubes 3 with a heat insultingmaterial 12;. In this zone, the temperature keeps dropping slowly sothat over the greatest possible length of the catalyzing material itkeeps at a temperature slightly higher than the temperature at which thecatalyzing material put in operation in this zone begins to act.

At the arrival of the gases at the end of this path, the maximumcontents in synthetic product is substantially obtained and the gasmixture is then subjected to a rapid cooling by a circulation in theexchanger closed by the inert material cylinders 14 surrounded by wiregauze or baffles 13.

The mixture of gases thus partly cooled comes out of the catalysis tubethrough 27 (at about Z50-300 C. for instance) to be cooled again stillmore outside and for the separation of the synthetic product.

The above devices, from their issuing from the zone of bell type tubesto the end of the cartridge, make it possible to effect, as in the zoneof the b-ell type tubes, a reaction which approaches a much moreconstant temperature than in former devices, the difference reachingpossibly C. It results therefrom a very important improvement in thelife of the catalyzing material, a better behaviour of the catalysisequipment and a very substantial improvement in the amount of thesynthesis product in the issuing gas, so than an important increase isobtained in the production per volume unit of the catalyzing materialused.

Figures 3 and 4 relate to a modification of the above apparatus in whichthe catalyzing material is placed in an annular chamber; lthe samenumerals indicate the same elements, but here, the space in which thegases to be reacted circulate is formed by the central space 16a, and bythe annular space 16, between the outer chamber and the wall of thecartridge 2. The result is that the mixture of the gases to be reactedand which has circulated in this central space 16a and the gases whichhave circulated throwgh the annular space 16 is effected only at theupper end of the cartridge at the very origin of the catalyzing materialin the chamber 28. The mixture of these two gases then `circulates as inthe above example in the inner tubes of the bell type tubes.

What I claim is:

1. An apparatus for the synthesis of ammonia by the passage of a gaseousmixture comprising nitrogen and hydrogen in their combining proportionsthrough a catalyst contained in reaction tubes comprising an externalclosed tube for resisting the pressure and provided with intake meansfor the gaseous mixture and discharge means for the gaseous mixture, anenvelope open at its lower end coaxial with the closed tube and havingits wall spaced from the internal surface of said tube, reaction tubesin said envelope, plates covering the upper and lower ends of saidreaction tubes, said tubes having intake and discharge ends andcontaining a catalyst except in a part thereof adjacent their dischargeends and disposed in Ithe envelope about its axis and parallel to saidaxis, each of said reaction tubes containing in a part of its lengthfrom the intake end to a region spaced from its intake end adistributing bell-type tubular section closed at its lower end andprovided with distributing orifices along the upper wall surfacesadjacent the intake end of the reaction tube, inner concentric tubesdisposed coaxially of the envelope and extending into the tubularsections adjacent the closed ends of the distributing bell-type tubularsections which are disposed within the catalyst-containing members, afeed tube extending into the lower end of the envelope through saidbottom closure plate between the reaction tubes for introducing theother part of the gaseous mixture into the envelope about the exteriorof the reaction tubes, said feed tube having its discharge locatedexteriorly .of and between the ends of the reaction tubes in thevicinity of the inner ends of the distributing bell-type tubularsections, and a central discharge tube concentric with said feed tubeextending from said catalyst-containing members.

2. An apparatus for the synthesizing of ammonia according to claim 1 inwhich the reaction tubes are provided with external baies which extendsubstantially over the par-t of their length, into Which thedistributing belltype tubular sections extend, and means for increasingthe exchange of heat on part of their length which is free of thecatalyst.

3. An apparatus for the synthesizing of ammonia according to claim 1 inwhich the reaction tubes are provided With internal baies in the mass ofthe catalyst, which is not in contact with the distributing bell-typetubular section.

8 4. An apparatus for the synthesizing of ammonia according to claim 3in which each reaction tube is surrounded by an external heat-insulatedlayer in the region between the terminal end of the catalyst mass andthe extreme bathe embedded in the catalyst.

References Cited in the tile of this patent UNITED STATES PATENTS UhdeAug. 25, 1936

1. AN APPARATUS FOR THE SYNTHESIS OF AMMONIA BY THE PASSAGE OF A GASEOUSMIXTURE COMPRISING NITROGEN AND HYDROGEN IN THEIR COMBINING PROPORTIONSTHROUGH A CATALYST CONTAINED IN REACTION TUBES COMPRISINGS AN EXTERNALCLOSED TUBE FOR RESISTING THE PRESSURE AND PROVIDED WITH INTAKE MEANSFOR THE GASEOUS MIXTURE AND DISCHARGE MEANS FOR THE GASEOUS MIXTURE, ANENVELOPE OPEN AT ITS LOWER END COAXIAL WITH THE CLOSED TUBE AND HAVINGITS WALL SPACED FROM THE INTERNAL SURFACE OF SAID TUBE, REACTION TUBESIN SAID ENVELOPE, PLATES COVERING THE UPPER AND LOWER ENDS OF SAIDREACTION TUBES, SAID TUBES HAVING INTAKE AND DISCHARGE ENDS ANDCONTAINING A CATALYST EXCEPT IN A PART THEREOF AJACENT THEIR DISCHARGEENDS AND DISPOSED IN THE ENVELOPE ABOUT ITS AXIS AND PARALLEL TO SAIDAXIS, EACH OF SAID REACTION TUBES CONTAINING IN A PART OF ITS LENGTHFROM THE INTAKE END TO A REGION SPACED FROM ITS INTAKE END ADISTRIBUTING BELL-TYPE TUBULAR SECTION CLOSED AT ITS LOWER END PROVIDEDWITH DISTRIBUTING ORIFICES ALONG THE UPPER WALL SURFACE ADJACENT THEINTAKE END OF THE REACTION TUBE, INNER CONCENTRIC TUBES DISPOSEDCOAXIALLY OF THE ENVELOPE AND EXTENDING INTO THE TUBULAR SECTIONSADJACENT THE CLOSED ENDS OF THE DISTRIBUTING BELL-TYPE TUBULAR SECTIONSWHJICH ARE DISPOSED WITHIN THE CATALYST CONTAINING MEMBERS, A FED TUBEEXTENDING INTO THE LOWER END OF THE ENVELOPE THROUGH SAID BOTTOM CLOSUREPLATE BETWEEN THE REACTION TUBES FOR INTRODUCING THE OTHER PART